Eccentric eyepiece for a firearm rear sight



SEARCH HUUWE Aug. 20, 1963 NJ. ANGELICA. 3,100,936

ECCENTRIC EYEPIECE FOR A FIREARM REAR SIGHT Filed May 25, 1961 Fig-i- INVENTOR! N 11 1 IAn 1' Hi BY 11: u 115 c|'e 1:11

United States Patent 3,100,936 ECCENTRIC EYEPIECE FOR A FIREARM REAR SIGHT Nicholas J. Angelica, Thompsonville, Conn., assignor to the United States of America as represented by the Secretary of the Army Filed May 23, 1961, Ser. No. 112,126 1 Claim. (Cl. 33-58) (Granted under Title 35, U.S. Code (1952), sec. 266) This invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention rel-ates to firearms and more particularly to rear sights therefor.

The standard rear sight for the U.S. Rifle cal. .30 M1 and the Springfield rifle M14 includes, as is well known in the art, an aperture member having an arcuate rack which is terminated at the top end by a circular lug provided with a peep sight aperture therethrough. The aperture member is actuatable to adjust the elevation angle of the sight by a pinion gear which has meshing engagement with the ck and which is rotatable by an adjustment knob. This adjustment knob is provided with a detent which is resiliently receivable by one of sixty radial, indexing grooves formed in the rifle receiver. The radius of the rack is such that, when the adjustment knob is rotated one click produced by the displacement of the detent into the next groove e angle of elevation of the sight is changed one minutell:

This degree of adjustment has een found to be that best suited for the military usage of the rifles but it is not fine enough when the rifles are used where exactness of sighting is imperative. This is because, when the angle of elevation is changed one minute, the center of bullet impact with a target one hundred yards away is changed one inch and, when the target is one thousand yards :away, the center of bullet impact is changed ten inches for each minute of elevation angle.

Therefore, the general object of this invention is to modify, without changing the proven structural qualities thereof, the standard rear sight of the U.S. Rifle Cal. .30 M1 and the Springfield Rifle M14, so that the angle of elevation is adjustable in increments of one-half minute, by rotatingly mounting on the aperture member an eyepiece which is journaled in a hole which is an enlargement of the peep sight aperture. The only other alteration of the standard rear sight is to eliminate the machining operation which rounds the lug around the peep sight aper-ture so that the lug retains the square s' formed in a previous manufacturing operation.

It is a more specific object of this invention to provide such a rotatable eyepiece in which the sighting aperture therein is eccentric to the axis around which the eyepiece is rot-ated so that the eyepiece is displaced to change the angle of elevation one-half minute when the eyepiece is rotated 180.

It is another object of this invention to locate the sighting aperture within a hood which provides both means for facilitating the rotation of the eyepiece and shading the sighting aperture to produce a sight picture which is clearer than that produced by the conventional peep sight aperture in the original aperture member.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

FIG. 1 is a longitudinally, cross-sectioned view of the modified rear sight mounted on a rifle receiver;

FIG. 2 is a view taken along line 22 of FIG. 1;

FIG. 3 is a view taken along line 33 of FIG. 2;

FIG. 4 is an enlarged, fragmentary, longitudinally, cross-sectioned view of the eyepiece; and

FIG. 5 is a perspective, exploded View of the aperture member and eyepiece.

Shown in the figures is a receiver 12 for the U.S. Rifie Cal. .30 M1 and a rear sight 14 mounted thereon. Rear sight 14 is the standard rear sight for the rifle except that an eyepiece 16 is rotatingly mounted on aperture member 18 to provide for adjustments of the elevation angle in increments of one-half minute as hereinafter described.

Aperture member 18, as is Well known in the art, has an arcuate rack 20 provided at the top end with a lug 22 which extends vertically upward from the top end thereof. Provided centrally through lug 22 is a longitudinal bore 24 in which eyepiece 16 is journaled for rotation as hereinafter described. Rack 20 is actuatable for displacing eyepiece 16 elevationally by the meshing engagement of the rack with a pinion 26 mounted on a lateral shaft 28 which is journaled in receiver 12 and is arranged to extend therethrough. Pinion 26 is manually rotated by a knob 30 fixed to the right end of shaft 28 outside of receiver 12. Provided on the inside of knob 30 is a detent 32 which is receivable in one of sixty radial grooves 33 equally spaced around shaft 28 in receiver 12 so that the knob is indexable with a click in one of sixty positions.

As rack 20 is arcuately formed, eyepiece 16 is provided with both a longitudinal and a vertical component of movement during actuation of the rack by knob 30. The radius of rack 20 is designed so that, when knob 30 is rotated one click, eyepiece 16 is vertically displaced one minute of elevation angle or .008 inch of vertical displacement.

Eyepiece 16 is cylindrical in configuration and has a longitudinal axis noted at xx. The front portion of eyepiece '16 is reduced in diameter concentric to axis x-x to form a bearing portion 34 which is matingly received by bore 24 and which is arranged to extend forwardly therethrough. Provided on hearing portion 34, where extending from bore 24, is an annular channel 35 which receives a split-type lock washer 36. -A cone-type spring 38 is mounted on bearing portion 34 between lock washer "36 and the front end of lug 22 to provide resilient rearward displacement of eyepiece 16 for a purpose to be noted hereinafter.

Bearing portion 34 extends rearward-1y to an annular shoulder 40 which forms the front end of the larger diameter portion of eyepiece 16 hereinafter referred to as hood 42. Hood 42 is concentrically bored from the rear end to an annular wall 44 disposed approximately midway the length of the hood. Provided in hood 42, approximately in the vertical plane coincident with annular shoulder 40, is a round sighting aperture 46 the center of which coincides with an axis yy which is disposed parallel to axis xx and is spaced vertically therefrom .002 inch (FIG. 4). Extending forwardly from wall 44 is a bore 48 which is concentric to axis y-y and which is terminated bya tapered hole 50, also concentric to axis y--y, which leads to sighting aperture 46. Another tapered hole 52 extends from sighting aperture 46 to the front end of bearing portion 34 to form a sighting tube 53 in which the sighting aperture is positioned intermediate the ends thereof.

A pair of Wells 54 extend longitudinally into hood 42 from annular shoulder 40 at diametrically opposite points therein and so that the axis of the wells and axis xx and y-y lie in the same plane and mounted in each of the walls is a spring-pressed ball 56. Balls 56 are receivable, respectively, by a pair of grooves 58 extending oppositely and vertically from bore 24 in lug 22, whereby eyepiece '16 is indexable in one of two sighting positions spaced 180 apart. The two sighting positions are identified by a V notch 60 cut in the front rim of hood 42 so as to be upwardly disposed When the center of sighting aperture 46 is disposed vertically above axis x-x (FIG. 2). The outside of hood 42 is serrated to facilitate the manual rotation thereof.

Thus, when eyepiece 16 is indexed with V notch 60 in the top position and the center of impact of a bullet with a target one thousand yards distant is five inches above target center, rear sight 14 is adjustable to correct the elevation by rotating 180 eyepiece 16 to where the spring-pressed balls 56 are received in the opposite ones of the grooves 58. Thereby, sighting aperture 46 is displaced from .002 inch aboveaxis xx to .002 inch below the axis for a total vertical displacement of .004 inch which is one-half the vertical displacement of eyepiece 16 when displaced by knob 30 one click, whereby the angle of elevation of rear sight 14 is changed one-half minute. Thus, as the center of impact of a bullet with a target located at a distance of one thousand yards is varied ten inches for each minute of change in the elevation angle, the 180 rotation of eyepiece 16 will lower the center of impact five inches to coincide with the target center, which would have been impossible with the conventional rear sight.

Besides providing means for easily rotating eyepiece 16, hood 42 also provides a better sight picture than is possible with the conventional sight because with sighting aperture 46 being located within the hood, the amount of light reflecting from the wall forming the sighting aperture is considerably reduced. Whereby, the wall of sighting aperture 46 is sharply defined so that the target is more easily centered therein.

Although a particular embodiment of the invention has been described in detail herein, it is evident that many variations may be devised within the spirit and scope thereof and the following claims are intended to include such variations.

I claim:

In a rear sight for a firearm with a receiver, the combination comprising an aperture member disposed for elevational displacement and including an arcuate rack and'a lug extending upwardly from one end thereof, a shaft extending through the receiver and journaled therein for rotation, a pinion fixed to said shaft for meshing engagement with said rack for elevational actuation thereof, an adjustment knob mounted on said shaft outside of the receiver to provide manual means for rotating said shaft, a detent disposed on said adjustment knob for resilient engagement with one of a plurality of grooves formed in the receiver around said shaft, said grooves being spaced and the radius of said aperture member being designed so that said lugis displaced elevationally a predetermined unit of elevational displacement when said adjustment knob is rotated to move said detent from one of said grooves to an adjacent onethereof, an eyepiece journaled in said lug for rotation around the longitudinal axis of said eyepiece, said eyepiece including a sighting tube located therein so that the longitudinal axis of said sighting tube is spaced from the longitudinal axis of the eyepiece a distance which is one-fourth the predetermined unit of elevational displacement, a sighting aperture located concentrically in said sighting tube and intermediate the ends thereof, a hood formed on the rear end of said eyepiece to shade the rear end of said sighting tube, and means for indexing said eyepiece in two sighting positions apart so that said sighting aperture is selectively positionable above and below the longitudinal axis of said eyepiece for changing the elevation of said sighting aperture one-half the predetermined unit of elevational displacement when said eyepiece is rotated 180.

References Cited in the file of this patent UNITED STATES PATENTS 1,035,124 Newitt Aug. 6, 1912 2,112,268 Burton Mar. 29, 1938 2,244,781 Johnson June 10, 1941 2,406,011 Garand Aug. 20, 1946 

